The present invention is related to the field of plastic material injection-molding.
Still more specifically, the invention is related to a method of injection-molding plastic material articles consisting of a plurality of components, comprising the steps of:
a) providing an injection molding machine having a stack mold in which a center platen on a first side thereof cooperates with a first mold portion via a first separation plane and, on a second side thereof cooperates with a second mold portion via a second separation plane, the stack mold being provided with a plurality of first, smaller cavities as well as with a plurality of second, larger cavities;
b) injection-molding of the first components of the plastic material article in first cavities located in the first separation plane;
c) unmolding the first components from the first cavities;
d) transferring the first components from the first separation plane to the second separation plane;
e) placing the first components into the second cavities;
f) injection-molding the second components on the first components within the second cavities; and
g) unmolding the plastic material articles from the second cavities.
The invention, further, is related to an apparatus for injection-molding plastic material articles consisting of a plurality of components comprising:
a) an injection molding machine having a stack mold in which a center platen on a first side thereof cooperates with a first mold portion via a first separation plane and, on a second side thereof cooperates with a second mold portion via a second separation plane, the stack mold being provided with a plurality of first, smaller cavities as well as with a plurality of second, larger cavities;
b) means for injection-molding
of the first components of the plastic material article in first cavities located in the first separation plane;
of the second components on the first components within the second cavities;
c) a handling system for
unmolding the first components from the first cavities;
transferring the first components from the first separation plane to the second separation plane;
placing the first components into the second cavities, and
unmolding the plastic material articles from the second cavities.
A method and an apparatus of the type specified before is disclosed in German patent specification 197 49 245 C2.
The invention, moreover, is related to a method for injection-molding plastic material articles in an injection molding machine having a mold in which at least one first mold portion cooperates with at least one second mold portion via at least one separation plane.
Finally, the invention is related to an apparatus for injection-molding plastic material articles in an injection molding machine comprising a mold in which at least one first mold portion cooperates with at least one second mold portion via at least one separation plane.
A method and an apparatus of the last-mentioned kind are generally known in the art.
Within the technology of plastic material injection-molding, it is well known to manufacture plastic material articles from a plurality of components. These various components may, e.g., consist of different plastic materials in order to take care of different requirements within different surface areas of the manufactured plastic material article. However, the various components may also consist of the same plastic material, however, being of a different color. By doing so, it is possible to manufacture multi-colored plastic material articles.
Various methods and apparatuses have been utilized for manufacturing such multi-component plastic material articles. It is, for example, well known to provide different hollow cavities or two groups of differently shaped hollow cavities, respectively, within one injection mold. In a first step, a first component of plastic material article is manufactured within the small hollow cavities by injection-molding. One may now transfer this component into the larger hollow cavity or, by appropriately displacing the mold one may configurate another hollow cavity above the component just manufactured. In any event, the second component of the plastic material article is directly injection-molded onto the first component in a further method step so that the two components are intimately adhered to one another.
It should be mentioned at this instance that the invention is not at all limited to the field of manufacturing multi-component plastic material articles. Instead, the invention may also be advantageously used for general applications, as long as areas of different temperature within the mold are concerned. The same applies for the use of stack molds which is also to be understood only as an example within the context of the present invention.
Published European patent application EP 0 903 213 A2 discloses various apparatuses and methods for manufacturing such plastic material articles. However, a technology is utilized in which an arm of a handling system or robot transversely enters into a gap between two mold portions of an injection mold when the latter is in its open operational position. After having entered between the mold portions, appropriate gripping elements transfer the components within the mold and unmold finished plastic material articles from the mold, respectively. In one of the shown and described embodiments (FIGS. 14A through 14L), a stack mold is utilized for that purpose. The term xe2x80x9cstack moldxe2x80x9d is to be understood to mean an injection-molding tool consisting of at least three portions, the center portion of which being identified as xe2x80x9ccenter platenxe2x80x9d within the art. The other two mold portions are located on opposite sides of the center platen. A stack mold, therefore, has at least two separation planes, namely on both opposite sides of the center platen in the transitory region to the two adjacent mold portions.
In the prior art apparatus, there is both a smaller and a larger hollow cavity within each separation plane. The two smaller hollow cavities are used for manufacturing the first component of the plastic material article as already mentioned above. The first components, when having been manufactured, are subsequently transferred to the larger hollow cavities and replete same by about one half. The second component is then directly injection-molded onto the first component within the larger hollow cavity.
The already mentioned robot arm is utilized for transferring the components and for unmolding the finished plastic material articles, respectively. The robot arm is adapted to be displaced in a transversal direction in the one or in the other separation plane and, moreover, may be displaced in a direction parallel to the opening or closing direction, respectively, of the mold so that it may be brought into positions where it is flush with the one or with the other separation plane, respectively.
During the transfer of the first component from the smaller hollow cavity to the larger hollow cavity, a change in separation plane is made in this prior art apparatus. Therefore, a first component having been manufactured within the first separation plane is then transferred into the larger hollow cavity in the other separation plane. For executing these transfers, the robot has a holding assembly on its free end. On both sides of the holding assembly, there are two grippers each for gripping components or work pieces, respectively, the grippers being configurated, for example, as suction heads. The grippers on each of the sides have a distance one from the other that is equal to the distance between the smaller and the larger hollow cavity within the two separation planes of the mold. The holding assembly may be pivoted by 180xc2x0 about an axis lying in the center between the two grippers and extending parallel to the direction of opening and closing of the mold. This prior art apparatus together with its associated method has two substantial disadvantages:
The first disadvantage consists in that each separation plane is provided with a large as well as with a small hollow cavity. This requires a complicated temperature control in the area of the two separation planes. As is well known in the art, one has to cool or to temperature-control injection molds during their operation in order to obtain optimum results. The requirements on such temperature control vary substantially depending on the size of the hollow cavity because the amount of heat brought into the hollow cavity highly depends on whether a larger or a smaller mass of liquid, i.e. very hot plastic material, is injected into various volumes of cavities.
A second disadvantage lies in the fact that a substantial amount of control is required due to the complicated reciprocal movements of the robot between the two separation planes which also implies relatively long transfer times However, in modern plastic material injection molding machines, this is highly undesired because the productivity of a plastic material injection molding machine highly depends on the cycle time. In the prior art apparatus and method discussed before, the cycle time to a high extent is determined by the displacement times of the handling systems, in particular of the robot arm when moved along the two necessary axes. Still worse, in the prior art apparatus, the stack mold is firstly opened only in the area of one separation plane for allowing the robot arm to enter into that separation plane, as the mold is still closed in the other separation plane. Only when the robot arm is about to enter into the second separation plane, the mold is also opened in the area of that second separation plane, however, it is then again closed in the area of the first separation plane. This requires a high amount of control in the area of the mold which is still more highly undesired because the mold may only be displaced relatively slowly due to its inherent inertia mass, in any event it is considerably slower as compared to the displaceable components of the handling system.
German patent specification 197 49 245 C1 mentioned at the outset discloses a method and an apparatus for injection-molding smart cards. Smart cards comprise a coil. For manufacturing the smart cards, a first card portion is injection-molded in a first hollow cavity. The coil is then applied to that first card portion. After having transferred the first card portion from the first hollow cavity to a second hollow cavity, a second card portion is injections-molded onto the first card portion, such that the coil is embedded between the two card portions. In a more general aspect, it is also disclosed in that specification that plastic material articles may be provided with items between two halves thereof or may be machined therebetween. Further (FIG. 23), a potential application is disclosed in which a stack mold is utilized for manufacturing these articles. In an open condition of the stack mold, a fork-type handling arm enters into the two gaps being open between the center platen on the one hand and the two lateral mold portions on the other hand, when the stack mold is in its open operational position. The handling arm unmolds the first part portions on the one side and transfers same to an external application station outside. the injection molding machine. When the coils have been applied to the first card portion, the first card portions are transferred to the other handling arm and, when the handling arm again enters into the mold, that handling arm enters into the second separation plane and places the card portions together with the coil into the larger hollow cavities which are located in that second separation plane.
It is, therefore, an object underlying the invention to provide a method and an apparatus of the type specified at the outset, such that the aforementioned disadvantages are avoided. In particular, the invention shall allow to simplify the design of the injection mold, to accelerate the process and, hence, to shorten the cycle time. Moreover, the reliability of the process and the quality of the plastic material articles so manufactured, shall be enhanced.
According to a first method of the type specified at the outset, this object is achieved in that the stack mold is temperature-controlled differently in the area of the first separation plane and in the area of the second separation plane.
According to a second method of the type specified at the outset, this object is achieved in that steps c), e) and g) are executed essentially independently one from the other.
According to a third method of the type specified at the outset, this object is achieved according to the invention in that the mold is temperature-controlled differently in different areas of the at least one separation plane.
According to a first apparatus of the type specified at the outset, the object underlying the invention is solved in that the stack mold in the area of the first separation plane and in the area of the second separation plane is provided with assemblies for different temperature-control.
In a second apparatus specified at the outset, the object underlying the invention is solved in that the handling system is provided with at least two arms adapted to be advanced into the first separation plane and into the second separation plane, respectively, essentially independently one from the other.
In a third apparatus of the type specified at the outset, the object underlying the invention is solved in that means are provided for temperature-controlling the mold differently in different areas of the at least one separation plane.
The object underlying the invention is thus entirely solved.
Namely, if, for example, all first hollow cavities are located within the first separation plane and all second hollow cavities are located in the second separation plane and a temperature control is effected of the type mentioned before, a highly simplified setting of the temperature within the mold is achieved. This is because one may optimize the temperature control for smaller hollow cavities alone within the one separation plane and for larger hollow cavities alone within the second separation plane. Accordingly, the masses within the mold become smaller and, hence, higher displacement speeds become possible, which, again, results in shorter cycle times.
If the various steps specified above are executed independently one from the other, in particular by utilizing a handling system having a plurality of arms adapted to enter into the mold simultaneously, the sequence of movements is simplified and likewise shortened so that, again, a contribution to the reduction of cycle time is made.
Seen as a whole, in the manufacture of plastic material articles consisting of a plurality of components in a stack mold, the invention yields substantial simplifications as compared to the prior art, both under apparatus aspects and under process aspects so that the cycle time may be substantially reduced.
The invention, further, has the advantage that due to the different temperature control and settings, the different sizes of hollow cavities within the separation planes may wholly be taken into account. This not only contributes to an increase in quality of the plastic material articles so manufactured. Further, in the area of a separation plane where a simpler temperature control assembly is sufficient, the design is simplified and the masses to be moved are reduced.
Finally, the invention has the advantage that when the arms are adapted to be moved independently from one another, individual processes may be executed, for example distinctly configurated arrangements of hollow cavities within the two separation planes may be approached individually.
According to a still further preferred improvement of the inventive method for injection-molding plastic material articles consisting of a plurality of components, a first component is firstly manufactured by injection-molding and then a second component is injection-molded on the first component, wherein the second component essentially encloses the first component.
This measure has, for example, the advantage that thick-walled articles may be injection-molded in a reliable manner, in that first a xe2x80x9cnucleusxe2x80x9d and then one or more shells or enclosures are injection-molded around the nucleus. when doing so, problems that would normally occur in connection with thick-walled articles do not occur, in particular with respect to the cooling down or the re-melting of surface areas.
In still another preferred improvement of this embodiment, the first component is essentially cylindrical and the second component surrounds the first component like a cylinder jacket or sleeve. As an alternative, one may also provide an article in which the second component goes through the first component,
These measures have the advantage that complex, in particular thick-walled articles, may be manufactured which, for example, may consists of the same or of two or more different plastic materials and/or of plastic materials of different color.
According to a preferred embodiment of the invention, the handling system is provided with a robot having arms, the arms, when the stack mold is open, being adapted to be advanced in a direction essentially perpendicular to the opening direction into gaps between the center platen and the first and the second mold portion, the arms extending essentially in the direction of advancement.
These measures have the advantage that a substantial reduction in time with respect to the necessary transfer steps within the injection mold become possible because the mold may be opened simultaneously in the area of the two separation planes and the handling system may also enter simultaneously into the two separation planes for then executing the required transfers. It is, therefore, no more necessary to displace the handling system in a direction parallel to the opening direction of the mold.
In any event, it is preferred under the present invention when a first arm adapted to be advanced into the first separation plane on one side thereof is provided with seats for first components, and a second arm adapted to be advanced into the second separation plane on both sides thereof is provided with seats for plastic material articles.
These measures have the advantage that also with respect to the necessary seats or grippers or holders, the design is as simple as. possible because the afore-described configuration is sufficient to effect all required transfer steps and to unmold the finished plastic material articles from the injection mold.
In a preferred improvement of this embodiment, the second arm comprises two sub-arms, the seats of the second arm being located on opposite sides of the sub-arms.
This measure has the advantage that for the seats oriented along the two directions like components configured as the two sub-arms may be utilized which only need to be mounted in opposite directions on the one arm.
According to another embodiment of the apparatus, a transfer station is provided for transferring the first components from the seats of the first arm into seats of the second arm.
This measure has the advantage that the robot may be put to a standstill during that phase, i.e. it is not necessary to displace same in a direction parallel to the opening direction of the mold. Instead, one only needs a relatively small and, hence, quickly displaceable transfer station effecting the transfer of the component quickly and safely.
This holds true in particular when the transfer station is adapted to be displaced in a direction perpendicular to the sides of the arms, wherein it is further preferred when the transfer station is located adjacent the first arm, the first components being adapted to be transferred from the first arm directed to the transfer station.
A particularly good effect is achieved in that case if after the transfer of the first components the first arm is adapted to be displaced out of the trajectory of the transfer station, the transfer station being adapted to be displaced into a position adjacent the second arm.
This measure, too, has the advantage that due to a minimized sequence of movements, i.e. by moving only those elements that absolutely need to be displaced, an extremely fast process becomes possible.
In another embodiment of the invention, however, one may also provide that the robot is adapted to be rotated about an axis extending parallel to the advancement direction, such that after rotation the first arm is flush with the second separation plane and the second arm is flush with the first separation plane.
Depending on the design of the injection molding machine and of the handling system, this embodiment may be advantageous under dynamical aspects.
In connection with this embodiment it is preferred when the second arm is adapted to be rotated about an axis extending parallel to the advancement direction.
This measure has the advantage that a fast transfer also becomes possible in the area of the second arm.
In all embodiments of the invention, it is preferred when a conveyor is provided for carrying away the plastic material articles in the area of the second arm.
This measure has the advantage that the plastic material articles may be transferred to the conveyor at a location where they are unmolded from the tool, for carrying them away subsequently as quickly as possible.
Depending on the configuration of the robot, the plastic material articles may be transferred to the conveyor from the second arm on the side opposite the first arm or from the second arm on the side facing the first arm.
Further advantages will become apparent from the description and the enclosed drawing.
It goes without saying that the features mentioned before and those that will be explained hereinafter may not only be used in the particularly given combination, but also in other combinations or alone without leaving the scope of the present invention.